Prior art bladder valves have suffered from various deficiencies, including being slow to open and close, inadequate sealing, obstructive flow passages, fragile bladders, and complexity of operation. In applications such as reverse pulse cleaning of filter elements it is important that there is a minimum pressure drop across the valve. It is also important that the valve is able to contain the relatively high pressure air used to provide the cleaning pulse, but will open rapidly so as to ensure a sharp peak pressure/energy pulse will pass through the valve to provide optimum cleaning effect. Prior art bladder valves have frequently not performed adequately, at least in some situations, for one or more of these reasons.
One known prior art bladder valve includes an inflatable bladder provided within a conduit in which liquids flow past the bladder. The bladder is loosely mounted within the conduit by a reinforced hook attached to a hose that is coupled to a source of pressurised air which is used to inflate the bladder to thereby close the valve and prevent passage of liquid through the conduit To deflate the bladder valve, air is removed from the bladder via the hose to thereby open the valve and allow liquid to flow through the conduit.
A problem with this prior art bladder valve is that the inflatable bladder is in direct contact with fluid flowing through the conduit which can cause wear and tear on the bladder.
Other bladder valves have a problem in that the bladder is asymmetrically mounted in the conduit in which it is located, and this can result in uneven opening, and thus a dissipated pressure/energy pulse passing through the valve.